The present invention relates to a maneuver device for an artificial satellite, which can greatly and speedily change an attitude angle and an angular velocity of the artificial satellite by means of an attitude control actuator such as a thruster and a reaction wheel mounted on the artificial satellite.
Artificial satellites are conventionally provided with a maneuver device which controls the attitude of the artificial satellite. FIG. 9 is a block diagram showing a configuration of an exemplary conventional maneuver device.
In the FIG. 9, the conventional maneuver device is provided with a feed forward torque instruction signal generator 107 for outputting a feed forward torque instruction signal 110 according to a pre-programmed maneuver plan, and a thruster 108 for generating control torque based on the input feed forward torque instruction signal 110 and applying the generated control torque to satellite dynamics 100. The satellite dynamics 100 represent the dynamic behavior of the artificial satellite incorporating this maneuver device. The maneuver device is further provided with an attitude angle detector 101 for detecting an attitude angle of the satellite dynamics 100 and outputting it as a detected attitude angle signal, an angular velocity detector 102 for detecting an angular velocity of the satellite dynamics 100 and outputting it as a detected angular velocity signal, a target attitude angle value generator 103 for generating a target value of the attitude angle of the satellite dynamics 100 and outputting it as a target attitude angle signal, and a target angular velocity value-generator 104 for generating a target value of the angular velocity of the satellite dynamics 100 and outputting it as a target angular velocity signal. The device is yet further provided with an attitude control signal calculator 105 for outputting an attitude control signal 111 based on inputs of an attitude angle error signal 112 (a difference signal between the target attitude angle signal and the detected attitude angle signal) and an angular velocity error signal 113 (a difference signal between the target angular velocity signal and the detected angular velocity signal), and a reaction wheel 106 for generating control torque based on the input attitude control signal 111.
Next, operations performed by this conventional maneuver device will be described. First, the feed forward torque instruction signal generator 107 generates a feed forward torque instruction signal 110 as torque to be applied to each axis of the satellite dynamics 100 at each time point according to the maneuver plan, and outputs the feed forward torque instruction signal 110 to the thruster 108. The thruster 108 is driven based on the input feed forward torque instruction signal 110 to generate and apply control torque to the satellite dynamics 100.
The feed forward torque instruction signal generator 107 outputs the feed forward torque instruction signal 110 according to the pre-calculated maneuver plan regardless of the state of the satellite dynamics 100. Thus, the accuracy of controlling the attitude may strikingly be deteriorated due to, for example, disturbance torque applied from the external environment to the satellite dynamics 100, an error of the feed forward torque instruction signal 110, an output error of the reaction wheel 106 and a control error caused by discrete outputs generated by the thruster 108.
The disturbance torque applied to the satellite dynamics 100 includes solar radiation pressure torque caused by pressure of sunlight, gravity gradient torque caused by gravity of the earth and the like, torque caused by control gas jet injected from the thruster striking against the artificial satellite (i.e., torque caused by a plume of the thruster), residual magnetic torque caused by interaction between the magnetism of the artificial satellite and the geomagnetic field, and aerodynamic torque caused by impact of a slight amount of aeromolecules existing in the orbit of the artificial satellite.
In order to compensate for attitude errors caused by such disturbance torque and control errors, the conventional maneuver device employs a system including the attitude angle detector 101, the angular velocity detector 102, the target attitude angle value generator 103, the target angular velocity value generator 104, the attitude control signal calculator 105, and the reaction wheel 106 which compensates for the attitude error during maneuver.
During the maneuver carried out by the feed forward torque instruction signal generator 107 and the thruster 108, the target attitude angle value generator 103 generates and outputs a target value of the attitude angle of the artificial satellite to the attitude control signal calculator 105 at each time point. At the same time, the target angular velocity value generator 104 generates and outputs a target value of the angular velocity of the artificial satellite to the attitude control signal calculator 105 at each time point. The attitude angle detector 101 detects the actual attitude angle of the artificial satellite and outputs it as a detected attitude angle signal to the attitude control signal calculator 105. At the same time, the angular velocity detector 102 detects the actual angular velocity of the artificial satellite and outputs it as a detected angular velocity signal to the attitude control signal calculator 105. Then, the attitude control signal calculator 105 generates an attitude control signal 111 based on an attitude angle error signal 112 generated as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal 113 generated as a difference signal between the target angular velocity signal and the detected angular velocity signal, and outputs the generated signal 111 to the reaction wheel 106. Here, the attitude control signal calculator 105 generates the attitude control signal 111 only with the input of the attitude angle error signal 112 and the angular velocity error signal 113, according to a generally-employed control logic such as PID (Proportional-plus-Integral-plus-Derivative) control rule. Then, the reaction wheel 106 is driven based on the attitude control signal 111 to generate and apply control torque to the artificial satellite. As a result, maneuver takes place in the satellite dynamics 100 while the attitude error caused by the thruster 108 during the maneuver is compensated by the control torque from the reaction wheel 106. The attitude of the satellite dynamics 100 is controlled during the maneuver by the sum of the control torque generated by the thruster 108 and the control torque generated by the reaction wheel 106.
FIG. 10 is a block diagram showing a configuration of another exemplary conventional maneuver device. The maneuver device shown in FIG. 10 represents those without a thruster. The configuration of the maneuver device shown in FIG. 10 differs from the maneuver device shown in FIG. 9 in that it has no thruster, and that a feed forward torque instruction signal 110 generated by a feed forward torque instruction signal generator 107 is added to an attitude control signal 111 generated by an attitude control signal calculator 105, and the resulting signal is input to a reaction wheel 106. Other than these differences, the configuration of the device shown in FIG. 10 is the same as that shown in FIG. 9.
In the maneuver device shown in FIG. 10, the reaction wheel 106 generates torque based on a sum signal of the feed forward torque instruction signal 110 and the attitude control signal 111, and uses the torque to perform maneuver. The maneuver device shown in FIG. 10 has an advantage in that it only uses the reaction wheel 106 as an attitude control actuator and thus can save an amount of fuel required by the thruster 108 (see FIG. 9). However, a maneuver rate that can be achieved decreases compared to that of the maneuver device shown in FIG. 9.
Thus, the conventional maneuver devices have the following problems. In the maneuver devices shown in FIGS. 9 and 10, the attitude control signal calculator 105 includes a PID controller and the like and thus requires a certain period of time to compensate for the above-mentioned attitude error. As a result, compensation for the attitude error cannot accurately follow the movement of the artificial satellite during the maneuver, and instead increases the attitude error. This also causes a problem that the setting time required becomes longer to achieve the target values of the attitude angle and the angular velocity for the maneuver. As long as the PID controller is used in the attitude control signal calculator 105, there is a limit to the improvement in the setting time (i.e., shortening of time), and thus cannot satisfy severe specification requirements.
In view of the above-described problems, the present invention has an objective of providing a maneuver device for an artificial satellite, in which an attitude error is small and setting time required to achieve a target attitude is short.
In one aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a thruster for generating control torque for driving the artificial satellite based on the feed forward torque instruction signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; a disturbance compensating signal calculator to which the feed forward torque instruction signal and the detected angular velocity signal are input, and which, in turn, outputs a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; and a reaction wheel to which the disturbance compensating signal is input, and which, in turn, generates control torque for driving the artificial satellite based-on-the input disturbance compensating signal.
According to the present invention, a disturbance compensating signal calculator is provided which estimates disturbance torque (torque other than the torque indicated by the feed forward torque instruction signal) based on a feed forward torque instruction signal for a thruster and a detected angular velocity signal, and outputs a compensating signal for the disturbance torque so that the artificial satellite will correctly obey the feed forward torque instruction signal. As a result, obedient errors of the attitude angle and the angular velocity during maneuver can be reduced and setting time required for maneuver can be shortened. The disturbance torque includes torque applied to the artificial satellite from the external environment such as solar radiation pressure torque, gravity gradient torque, torque caused by a plume of the thruster, residual magnetic torque and aerodynamic torque, as well as torque caused by an error of the feed forward torque instruction signal, an output error of the reaction wheel and a control error caused by discrete outputs generated by the thruster.
In another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a thruster for generating control torque for driving the artificial satellite based on the feed forward torque instruction signal; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; a disturbance compensating signal calculator to which the feed forward torque instruction signal and the detected angular velocity signal are input, and which, in turn, outputs, to a reaction wheel, a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; and the reaction wheel which generates control torque for driving the artificial satellite based on the attitude control signal and the disturbance compensating signal.
The device of the invention is provided with the attitude control signal calculator, which, together with the disturbance compensating signal calculator, is able to reduce the obedient errors of the attitude angle and the angular velocity during maneuver and to shorten the setting time required for maneuver. In the artificial satellite maneuver device of the invention, disturbance torque applied to the artificial satellite is estimated based on the feed forward torque instruction signal and the angular velocity of the artificial satellite corresponding to the feed forward torque instruction signal. Therefore, a disturbance compensating signal which is supposed to compensate for this estimated disturbance torque contains a signal that eliminates the effect of the attitude control signal. For this reason, the disturbance compensating signal could deteriorate and cancel control accuracy of the attitude control signal calculator. Since the present invention aims at keeping the actual movement of the satellite to obey the target movement indicated by the feed forward torque instruction signal, it can be neglected even if the effect of the attitude control signal calculator is weakened.
In yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; a sum signal calculator to which the feed forward torque instruction signal and the disturbance compensating signal are input, and which, in turn, outputs a sum signal of these input signals at a predetermined timing; a thruster for generating control torque for driving the artificial satellite based on the sum signal; and an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal. The sum signal and the detected angular velocity signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.
In still yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite; a sum signal calculator to which the feed forward torque instruction signal and the disturbance compensating signal are input, and which, in turn, outputs a sum signal of these input signals at a predetermined timing; a thruster for generating control torque for driving the artificial satellite based on the sum signal; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; and a reaction wheel for generating control torque for driving the artificial satellite based on the attitude control signal. The sum signal and the detected angular velocity signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.
In still another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a thruster for generating control torque for driving the artificial satellite based on the feed forward torque instruction signal; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; a sum signal calculator to which the attitude control signal and the disturbance compensating signal are input, and which, in turn, outputs a sum signal of these input signals at a predetermined timing; and a reaction wheel for generating control torque for driving the artificial satellite based on the input sum signal. The difference signal between the detected angular velocity signal and the target angular velocity signal as well as the sum signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.
In the artificial satellite maneuver device of the invention, disturbance torque applied to the artificial satellite is estimated based on a sum signal of the attitude control signal and the disturbance compensating signal as well as a difference signal between the detected angular velocity signal and the target angular velocity signal. Therefore, potential canceling relationship between the attitude control signal calculator and the disturbance compensating signal calculator can be improved while keeping the actual movement of the artificial satellite to follow the movement indicated by the feed forward torque instruction signal. The advantage of the disturbance compensating signal calculator can be taken out as an output as much as possible. As a result, the characteristic of the artificial satellite to achieve the target movement can be improved, and highly accurate response can be obtained even in the course of maneuver.
In yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; a disturbance compensating signal calculator to which the feed forward torque instruction signal and the detected angular velocity signal are input, and which, in turn, outputs a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; and a reaction wheel for generating control torque for driving the artificial satellite based on the disturbance compensating signal and the feed forward torque instruction signal.
According to the present invention, even when a thruster is not used, compensation can be carried out with the disturbance compensating signal by using only the reaction wheel.
In yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; a disturbance compensating signal calculator to which the feed forward torque instruction signal and the detected angular velocity signal are input, and which, in turn, outputs a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; and a reaction wheel for generating control torque for driving the artificial satellite based on the attitude control signal, the disturbance compensating signal and the feed forward torque instruction signal.
In another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; a sum signal calculator to which the feed forward torque instruction signal and the disturbance compensating signal are input, and which, in turn, outputs a sum signal of these input signals at a predetermined timing; and a reaction wheel for generating control torque for driving the artificial satellite based on the sum signal. The sum signal and the detected angular velocity signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.
In yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; a sum signal calculator to which the feed forward torque instruction signal and the disturbance compensating signal are input, and which, in turn, outputs a sum signal of these input signals at a predetermined timing; and a reaction wheel for generating control torque for driving the artificial satellite based on the sum signal and the attitude control signal. The sum signal and the detected angular velocity signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.
In still yet another aspect of the invention, a maneuver device for an artificial satellite comprises: a feed forward torque instruction signal generator for outputting feed forward torque instruction signals as a profile of torque to be applied to the artificial satellite according to a maneuver plan; a target attitude angle value generator for generating and outputting a target value of an attitude angle of the artificial satellite as a target attitude angle signal; a target angular velocity value generator for generating and outputting a target value of an angular velocity of the artificial satellite as a target angular velocity signal; an attitude angle detector for detecting and outputting an attitude angle of the artificial satellite as a detected attitude angle signal; an angular velocity detector for detecting and outputting an angular velocity of the artificial satellite as a detected angular velocity signal; an attitude control signal calculator to which an attitude angle error signal as a difference signal between the target attitude angle signal and the detected attitude angle signal as well as an angular velocity error signal as a difference signal between the target angular velocity signal and the detected angular velocity signal are input, and which, in turn, outputs an attitude control signal; a disturbance compensating signal calculator for outputting a disturbance compensating signal for compensating for disturbance torque applied to the artificial satellite during maneuver; a sum signal calculator to which the attitude control signal and the disturbance compensating signal are input, and which, outputs a sum signal of these input signals at a predetermined timing; and a reaction wheel for generating control torque for driving the artificial satellite based on the sum signal and the feed forward torque instruction signal. The sum signal and the difference signal between the detected angular velocity signal and the target angular velocity signal are input to the disturbance compensating signal calculator, which, in turn, generates and outputs a new disturbance compensating signal at a predetermined timing.